1. Field of the Invention
The present invention relates to an ink jet recording apparatus which is applied to, for example, a printer or a facsimile machine and which discharges ink from a nozzle opening.
2. Description of the Related Art
Up to now, an ink jet recording apparatus has been known in which an ink jet head for discharging ink from plural nozzles is used to record characters and images on a recording medium. In such an ink jet recording apparatus, the ink jet head opposite to the recording medium is fixed to a head holder, the head holder is mounted to a carriage, and scanning is performed in a direction perpendicular to a conveying direction of the recording medium.
FIG. 9 is a schematic exploded view of an example of an ink jet head used in such an ink jet recording apparatus, and FIGS. 10A and 10B are sectional views of a main part of the ink jet head. As shown in FIG. 9 and FIGS. 10A and 10B, in a piezoelectric ceramic plate 201, plural grooves 202 are arranged in parallel with each other and are separated from one another by side walls 203. One end portion of each groove 202 in a longitudinal direction thereof is provided so as to extend to one end surface of the piezoelectric ceramic plate 201 while the other end portion is not extended to the other end surface and gradually becomes shallow. Further, electrodes 205 for application of a driving electric field are formed on surfaces on the opening side of both side walls 203 of each groove 202 in the longitudinal direction.
A cover plate 207 is jointed to the opening side of the grooves 202 of the piezoelectric ceramic plate 201 through an adhesive 209. The cover plate 207 is provided with: an ink chamber 211 that is a concave portion communicated with the shallow other end portion of each groove 202; and an ink supply port 212 that penetrates a bottom portion of the ink chamber 211 in an opposite direction to the grooves 202.
Further, a nozzle plate 215 is jointed to an end surface, which is opened with the grooves 202, of a joint member of the piezoelectric ceramic plate 201 and the cover plate 207. Nozzle openings 217 are formed at positions, which are opposite to the respective grooves 202, in the nozzle plate 215.
Note that a wiring substrate 220 mounted with, for example, a driving circuit having a driving IC and the like, is fixed onto a surface, which is on the opposite side to the cover plate 207, of the piezoelectric ceramic plate 201 on the opposite side to the nozzle plate 215. In the wiring substrate 220, wirings 222 connected to the respective electrodes 205 through bonding wires 212 or the like are formed, and a driving voltage can be applied to the electrodes 205 through the wirings 222.
In the ink jet head structured as described above, when ink is filled into the respective grooves 202 from the ink supply port 212, and a predetermined driving electric field is made to act on both the side walls 203 of the predetermined groove 202 through the electrodes 205, the side walls 203 are deformed to vary a volume in the predetermined groove 202, as a result of which an ink droplet in the groove 202 is discharged from the nozzle opening 217.
For example, as shown in FIG. 11, in the case where ink is discharged from the nozzle opening 217 corresponding to a groove 202a, a positive driving voltage is applied to electrodes 205a and 205b in the groove 202a, and also, electrodes 205c and 205d respectively opposite thereto are made to be grounded. Thus, a driving electric field in a direction toward the groove 202a acts on side walls 203a and 203b. When the driving electric field is perpendicular to a polarization direction of the piezoelectric ceramic plate 201, the side walls 203a and 203b are deformed in the direction of the groove 202a due to a piezoelectric thickness slide effect. Thus, a volume in the groove 202a is reduced to increase a pressure. As a result, the ink droplet is discharged from the nozzle opening 217.
In attaching the above-described ink jet head to an ink jet recording apparatus, driving conditions of the ink jet head, for example, a so-called voltage rank that indicates a magnitude of a driving voltage to be applied to electrodes in each groove, a type of ink to be used, and resolution, need to be set for each ink jet head.
For example, the voltage rank depends on a thickness of a side wall of each groove, and thus differs for each ink jet head due to a manufacturing error or the like. Further, as to identical ink jet heads as well, the voltage rank differs depending on a type of ink to be used, that is, oil-based ink, aqueous ink, or the like. For example, the case of the oil-based ink adopts a voltage of 20 to 24 V, and the voltage rises by approximately 3.0 V when the side wall becomes thick by 4.0 μm.
Therefore, according to the prior art, in, for example, the product shipment of ink jet heads, the ink jet heads are individually managed by being attached with labels each showing a voltage rank. Further, in attaching the ink jet head to an ink jet recording apparatus, setting is performed manually while an operator checks the voltage rank written in the label.
Accordingly, there is a problem in that an operation for managing and setting a voltage rank for each ink jet head becomes complicated. Further, the voltage rank needs to be set in each case of shipment or exchange of an ink jet head, which is extremely troublesome. In addition, there is a problem in that a setting error is caused by manually setting the voltage rank for each ink jet head.
Further, there is a problem in that most of ink jet-head users do not know a the lifetime of the head, and in the case where performance of the head, for example, an ink discharge characteristic is deteriorated, it is difficult for the users to make a judgment on whether the cause of the deterioration is the expired lifetime or the failure of the head. On the other hand, there is a problem in that a manufacturer does not know the head usage status on the user side and thus, it is relatively difficult for the manufacturer to discover the cause of the head failure.
It is noted that in the case where the identical ink jet head is used to the end of its lifetime without exchange, the usage status of the head can be grasped with relative ease. Thus, when a problem arises in performance of the head, a projection can be made as to which is the cause between, for example, the lifetime of the head or other factors. However, most users use plural ink jet heads while the heads are replaced with one another, and thus, it is very difficult that the usage status is managed to be grasped for each head. Further, there is also a case where, depending on the user, different types of ink are used with the identical head while being replaced with one another. Therefore, it is very difficult to discover the cause of the head failure.